Infrared Imaging for Sleep Apnea Diagnosis Shows Promise, Study Says

New research presented at CHEST 2007, held Oct. 20-25 in Chicago, shows that remote infrared imaging can monitor airflow and accurately detect abnormalities during sleep without ever coming in contact with the patient. Infrared imaging is ideal for detecing sleep apnea, the study said, because it is portable and can monitor sleep in a natural environment.

“Polysomnography is a diagnostic test, which establishes the presence or absence of sleep disorders. But standard methods have the potential to significantly disturb a patient’s sleep pattern, so what we see in the lab may not be a true representation of the patient’s sleep habits,” said lead study author Jayasimha Murthy, MD, assistant professor of medicine, University of Texas Health Science Center at Houston.

“However, remote infrared imaging is a non-contact method, so there is minimal interference with the patient. In fact, this system can be designed to where the patient isn’t even aware that monitoring is taking place,” Murthy said.

In the study, Murthy and colleagues from the University of Texas Health Science Center at Houston, the University of Houston and Memorial Hermann Sleep Disorders Center in Houston evaluated the efficacy of remote infrared imaging (IR-I) in 13 men and women without known sleep apnea.

Researchers recorded the heat signals expired from patients’ nostrils or mouth using an infrared camera during one hour of polysomnography. To minimize any bias, airflow channels were recorded and analyzed separately. Results were then compared with those obtained through the conventional methods of sleep apnea diagnosis, including nasal pressure, nasal-oral thermistors and capnography.

“The underlying principle of monitoring the relative changes in airflow based on the changing of the infrared heat signal is similar to that of the traditional thermistor,” Murthy explained. “However, the biggest difference is that the thermistor is placed in the subject’s nostril while the infrared camera is placed 6 to 8 feet from the patient’s head. Also, this method allows us to have recorded data, so we can go back and extract the airflow data after the completion of the study, which we can’t do with conventional sensors.”

Results showed that IR-I detected 20 sleep-disordered breathing events, compared with 22 events detected by the nasal-oral thermistor, and 19 events detected by nasal pressure. Given the outcome, researchers suggested that IR-I represents a non-contact alternative to standard nasal-oral thermistors.

“The results from this study will greatly impact the development of this technology,” Murthy said. “While implementation of this technology for clinical studies is still far away, these early results are encouraging enough for us to pursue this further.”

Other findings presented at CHEST 2007, the 73rd annual international scientific assembly of the American College of Chest Physicians, include the following:

First-Night Comfort May Determine Future CPAP Use

How a patient with obstructive sleep apnea feels on their first night using a continuous positive airway pressure machine may determine their future compliance, according to a new study from the Cleveland Clinic.

Researchers administered behavioral questionnaires to patients prescribed continuous positive airway pressure therapy, and determined compliance via a meter within the machine, which measured length of use. Results showed a positive correlation between CPAP compliance and patients’ level of comfort and ease on the first night of use.

Researchers also found that patients who recently experienced the death of a loved one were less likely to comply.

Poor Bedtime Behaviors More Common in OSA

New research shows patients with obstructive sleep apnea have worse bedtime behaviors than people who do not suffer from the condition.

Researchers from MetroHealth Medical Center in Ohio administered behavioral questionnaires to more than 500 patients with and without OSA. They found that patients with OSA were more likely to exhibit poor sleep hygiene and less likely to sleep in a bed.

The research suggests such alternative sleeping environments may impact sleep duration and overall health status.

Fragmented Sleep Affects Cholesterol

Researchers from the University of Pittsburgh School of Medicine have released a new study examining the relationship between sleep fragmentation and lipid profiles. Both normal and overweight individuals underwent three nights of testing, which included polysomnography and blood testing to determine total cholesterol and triglycerides.

Results showed that moderate sleep fragmentation was associated with reduced cholesterol in the study’s overweight participants only.

Neck Size Is Best Predictor of Sleep Apnea Severity

A new study evaluates the roles of gender and body measurements in the severity of OSA and CPAP requirements.

Researchers from Baylor College of Medicine and The Methodist Hospital in Texas took multiple body measurements from 144 men and women with OSA. They found that patients’ neck circumference, rather than their body mass index, was more predictive of OSA severity, especially in women. Both neck circumference and BMI correlated to CPAP requirements.

CPAP May Help Manage Irregular Heartbeat

Body mass index (BMI) and apnea hypopnea index (AHI) show no relation to premature ventricular arrhythmias PVC) in patients with obstructive sleep apnea, according to a new study.

However, the researchers, from Lutheran Medical Center and SUNY-Downstate Medical Center in New York, said that treatment with CPAP decreases the incidence of both AHI and PVC. The significant decrease in PVC may be the result of decreased transmural pressure, the researchers said.

Female Sexual Dysfunction Linked to Sleep Apnea

While sexual dysfunction in men with obstructive sleep apnea is well described, it has not been previously reported in women. Researchers from the Baylor College of Medicine in Texas administered sexual function questionnaires to 21 premenopausal women with OSA who were referred to a sleep lab.

Researchers found a high prevalence of sexual dysfunction in the women that was unrelated to body mass index or negative mood.

Night Shift Nurses Sleepier than Day Shift Nurses

A new study suggests that, despite the amount of sleep night shift nurses receive, they are more likely to experience sleepiness when compared with their day shift counterparts.

Researchers from Texas A&M University, Baylor College of Medicine and the Torr Sleep Center measured the amount of sleep received by day and night shift nurses using actigraphy. The nurses also answered questions related to the effects of sleepiness.

Results showed that although both groups of nurses received the same amount of sleep, the night shift nurses were more likely to experience sleepiness.

For more from CHEST 2007, visit www.chestnet.org.